1. Field of the Invention
This invention relates to a method and apparatus for reducing oxides of nitrogen in the exhaust emissions of an internal combustion engine, and more particularly, to a new and improved spark discharge device for forming atomic (monatomic) nitrogen from molecular nitrogen so that the atomic nitrogen can be injected into the exhaust of an internal combustion engine to reduce oxides of nitrogen in the exhaust to nitrogen and oxygen.
2. Background of the Invention
If oxygen enriched air is used as part of the intake of an internal combustion engine, the engine's power density tends to be increased and the particulate emissions from the engine tend to be reduced. On the other hand, the use of such oxygen enriched air tends to increase the amount of oxides of nitrogen (NO.sub.X) that are present in the engine's exhaust. This increase in the amount of NO.sub.X in the engine's exhaust has concerned developers and manufacturers of internal combustion engines because legal regulations dealing with emissions from an internal combustion engine include specifications limiting the amount of NO.sub.X that may be present in such emissions. Consequently, the developers and manufacturers of internal combustion engines would like to obtain the advantages of using oxygen enriched air in the intake of an internal combustion engine, but at the same time would like to reduce the amount of NO.sub.X that is present in the engine's emissions.
One way of reducing NO.sub.X in any stream of gas is to inject atomic nitrogen into the stream of gas. For example, an article entitled "Effect of nitrogen-containing plasmas on stability, NO formation and sooting of flames" by J. C. Hilliard and F. J. Weinberg appearing in Nature, Vol. 259, page 556 (Feb. 19, 1976) indicates that nitrogen atoms from a plasma can be injected into a fast flowing stream of nitric oxide in argon and synthetic exhaust gas mixes. The article further states (page 557) that "[r]eductions in nitric oxide from 3,000 p.p.m. to a residual 80 p.p.m. were readily obtained in flows up to 250 l min.sup.-1." In German Patent Application No. DE 34 09 859 A1, which was filed Mar. 17, 1984, was published Sep. 19, 1985, and is entitled "Denitration of Waste Gases", the NO.sub.X in the waste gases from combustion engines and plants is formed into nitrogen and oxygen by introducing nitrogen atoms into the flow of such waste gases. In that German patent application, the amount of nitrogen atoms introduced into the waste gas stream is dependent on the NO concentration measured upstream and downstream of the generator of the nitrogen atoms.
One problem associated with the injecting of atomic nitrogen into the exhaust of an automobile engine is providing a source of nitrogen from which the atomic nitrogen can be formed. One of the most common sources from which atomic nitrogen can be formed is ammonia (NH.sub.3), but at the present time, it is not practical to store ammonia in an automobile. Even if a source of molecular nitrogen is available, an additional problem associated with the injection of atomic nitrogen into the exhaust of an automobile engine is the forming of the atomic nitrogen. A sufficient quantity of atomic nitrogen has to be produced in order to reduce the NO.sub.X in the exhaust of an automobile engine to nitrogen and oxygen. However, the atomic nitrogen needs to be produced in or in close proximity of the exhaust stream because atomic nitrogen tends to be unstable.
Accordingly, it is an object of the present invention to provide a new and improved method and apparatus for forming atomic nitrogen from molecular nitrogen so that the atomic nitrogen can be injected into the exhaust of an internal combustion engine to thereby reduce oxides of nitrogen in the exhaust to nitrogen and oxygen.
It is another object of the present invention to provide a new and improved spark discharge device for producing atomic nitrogen in or near the exhaust of an internal combustion engine so that the oxides of nitrogen present in that exhaust will be reduced to nitrogen and oxygen as the atomic nitrogen is so introduced into the exhaust.
It is yet another object of the present invention to provide a new and improved method and apparatus for reducing the amount of NO.sub.X in the emissions from an internal combustion engine by utilizing a modified automotive spark plug to produce a pulsating spark in a spark gap that forms atomic nitrogen from nitrogen enriched air that is produced by a selectively permeable membrane and is introduced into the spark gap so that the atomic nitrogen can be introduced into the exhaust of an internal combustion engine.